Recently, the preparation and distribution of promotional game cards, premium cards, lottery tickets and the like, containing hidden messages or symbols has become popular and widespread, in fund raising and product promotion. The recipient of such a card must remove from the card a layer of hiding coating in order to reveal a message or symbol. Such items are, however, difficult to prepare and print in an economical fashion, because of the technical specifications they must fulfill.
Such a card bearing a hidden message normally has at least two coating layers overlying a hidden message. Immediately over the message, a transparent or translucent protective layer is provided, through which the message can be read. Over the protective layer, an opaque second layer ("hiding layer") is applied in order to hide the message. The hiding layer can be subsequently stripped away e.g. by scratching etc., to reveal the message through the first coat.
It is necessary that there exists, as between the protective coat or layer and the hiding coat or layer an acceptable degree of adhesion or affinity, so that the hiding coat remains in place and opaque to hide the message during storage, shipping, packaging and transportation of the cards. Nevertheless, the hiding coat ("scratch-off coat") must be readily removable by abrasion by the user at the required time, to render the message visible, leaving the first coat susbtantially unaffected.
Effectively, one must satify two essentially contradictory requirements in the relationship between the varnish coat and the hiding coat, to render them mutually compatible and adhesive to one another at one time, and imcompatible and non-adhesive to one another at another time.
Heretofore, these mutually inconsistent requirements have been satisfied by using a thick hiding coat applied by silk screen methods, over a thin varnish coat applied by lithographic methods or by silk screen methods. In view of its thickness and consistency, the only practical way of applying the hiding coat is by silk screening. This is costly and inconvenient. Lithography is the cheapest, fastest way of printing and applying coatings to such cards. To have to apply one coating by lithography and the other coating by silk screening entails the transfer of the card stock from one printing machine to another, or even the transferring from one printing plant to another printing plant, with consequent added inconvenience, extra expense and loss of security.